The present invention concerns a cleaning agent used in a process for manufacturing a semiconductor device and a method of manufacturing a semiconductor device.
In the process of manufacturing a semiconductor device, an etching fabrication technique utilizing chemical reaction has been used as a method of forming a wiring structure on a semiconductor substrate by using a conductive material.
Generally, a method of initially applying a mask fabrication technique by photoresist and then removing a non-masked portion by using a chemical or a reactive gas has been practiced. In the semiconductor industry in recent years, the tendency toward a high degree of integration requires microscopic processing. In particular, the fabrication of metal film wirings has been demanded more and more and a fabrication technique aiming for an accuracy of less than 0.5 um has been demanded for present-day semiconductor devices.
In order to attain such a degree of accuracy, improvement in the fabrication accuracy where a photoresist mask is employed and improvement in the dry etching technique for removing the non-masked portion are necessary. Referring particularly to the use of photoresist material, conventional positive or negative type resists of a single layered structure, as well as a multi-layered resist structure using a combination of resist and other resins have been used.
Further in the dry etching technique, anisotropic etching has been advanced with the establishment of a technique for providing side wall protecting deposition films by using the photoresist and reactive gases and etching at higher selectivity.
As a disadvantage accompanying the establishment of such techniques, there can be mentioned an extreme difficulty in the method of removing the side wall protecting deposition films and the corrosion of metal wiring materials. If the side wall protecting deposition film has not been removed sufficiently, radicals or ions in the reaction gas incorporated into the side wall protecting deposition film react with intaken moisture to form an acid when left in air after the completion of the etching procedure. The thus-formed acid results in corrosion of wiring materials to bring about significant undesired effects such as an increase in resistance and breaks in the wire. Particularly, such a phenomenon frequently occurs, for example, in aluminum and aluminum alloy used generally as the wiring material.
For preventing such corrosion, a method has been adopted involving the washing out of chlorine radicals or ions by applying highly purified water for cleaning purposes over a long period of time after dry etching. However, it is extremely difficult to completely remove chlorine ions or radicals from the side wall protecting deposition film by this method, so that the problem of corrosion can not be avoided completely. Accordingly, complete removal of the side wall protecting deposition film would be required in order to thoroughly prevent the corrosion.
For removing such a side wall protecting deposition film, a resist cleaning agent of an acidic organic solvent or a resist cleaning agent of an alkaline organic solvent has been used.
As the resist cleaning agent of the acidic organic solvent, a cleaning agent prepared by adding a phenol compound, chloro solvent or aromatic hydrocarbon to alkylbenzene sulfonic acid has generally been used. However, it is not possible to completely remove the side wall protecting deposition film even by applying a heat treatment at a temperature of higher than 100xc2x0 C. by using this cleaning agent. Further, since the resist cleaning agent of the acidic organic solvent is less soluble in water, it is necessary to clean with an organic solvent such as iso-propanol having good solubility with water after the removing operation and then wash with water, which however complicates the process.
On the other hand, it is also rather difficult to remove the side wall protecting deposition film by using the resist cleaning agent of the alkaline organic solvent even by heating to a temperature higher than 100xc2x0 C. like that of an acidic cleaning solution. As described above, since the side wall protecting deposition film can not completely be removed using either the acidic or alkaline cleaning agent, occurrence of corrosion caused by residual chlorine radicals or ions is inevitable.
As a method different from the cleaning method described above, there has been known a method of removing the residual resist after plasma ashing by using an alkaline aqueous solution such as a positive type resist developing solution containing tetramethyl ammonium hydroxide (Japanese Patent Laid-Open Sho 62-281332). However, a conductive layer made of an aluminum-containing substance is violently eroded with the alkaline aqueous solution in this method.
Further, for the protecting deposition film formed upon dry etching of a titanium or tungsten layer, a method of removing the film has not yet been established. The titanium or tungsten layer is often used as metal wirings for an intermediate layer upon making a conductive layer into a multi-layered structure in a semiconductor device.
If the resultant side wall protecting deposition film is left as it is, adjacent wirings are brought into contact by the side wall protecting deposition film, for example, due to pressure of the deposition film in the succeeding step to cause a short-circuit or an abnormality in the wirings.
As has been described above, while various methods have been employed in a production process for a semiconductor device for removing the side wall protecting deposition film formed on the side walls of the conductive layer or removing photoresist formed on the semiconductor substrate, there is a problem such as the occurrence of corrosion of the metal wiring and it is required for a cleaning agent for a semiconductor device to be capable of easily removing the side wall protecting deposition film, while not causing corrosion of the metal conductive layer upon cleaning.
It is an object of the present invention to provide a cleaning agent for a semiconductor device capable of easily removing a side wall protecting deposition film formed by dry etching, while causing no corrosion to a conductive layer made of various kinds of metal material as the wiring material and not resulting in corrosion at all, as well as a method of manufacturing a semiconductor device capable of manufacturing circuit wirings at a high level of accuracy.
In accordance with the present invention, it has been determined that a cleaning agent for a semiconductor device comprising an aqueous solution containing a quarternary ammonium salt and a fluoro compound or an aqueous solution containing a quarternary ammonium salt and a fluoro compound, as well as an organic solvent selected from the group consisting of amides, lactones, nitrites, alcohols and esters exhibits excellent characteristics having a property of removing a side wall protecting deposition film formed upon dry etching, corrosion inhibitive property, and possesses a non-corrosive nature with respect to wiring materials and good operation performance.
That is, the present invention provides a cleaning agent for a semiconductor device comprising a quarternary ammonium salt represented by the general formula:
[(R1)3Nxe2x80x94R]+.Xxe2x88x92
in which R represents an alkyl group of 1 to 4 carbon atoms or a hydroxyl substituted alkyl group of 1 to 4 carbon atoms, R1represents an alkyl group of 1 to 4 carbon atoms and X represents an organic or inorganic acid group, and a fluoro compound.
The present invention further provides a cleaning agent for a semiconductor device, wherein from 1 to 50% by weight of one or more of organic solvents selected from amides, lactones, nitrites, alcohols and esters are present in addition to the quarternary ammonium salt and the fluoro compound.
The present invention further provides a method of manufacturing a semiconductor device by forming a mask with a photoresist on a conductive layer formed on a semiconductor substrate, wherein the conductive layer contains at least one of titanium, tungsten, aluminum and aluminum alloy and then forming a wiring structure by dry etching, wherein the method includes a cleaning step of peeling a protecting deposition film formed on side walls for the conductive layer and the photoresist by using a cleaning agent for a semiconductor device comprising a quarternary ammonium salt represented by the general formula:
[(R1)3Nxe2x80x94R]+.Xxe2x88x92
which R represents an alkyl group of 1 to 4 carbon atoms or a hydroxyl substituted alkyl group of 1 to 4 carbon atoms, R1represents an alkyl group of 1 to 4 carbon atoms and X represents an organic or inorganic acid group, and a fluoro compound.
The quarternary ammonium salt represented by the foregoing general formula can include, for example, tetramethyl ammonium formate, tetramethyl ammonium acetate, tetramethyl ammonium propionate, tetramethyl ammonium butyrate, tetramethyl ammonium oxalate, tetramethyl ammonium malonate, tetramethyl ammonium maleate, tetramethyl ammonium fumarate, tetramethyl ammonium citraconate, tetramethyl ammonium benzoate, tetramethyl ammonium toluate, tetramethyl ammonium phthalate, tetramethyl ammonium acrylate, trimethyl(2-hydroxyethyl)ammonium formate, trimethyl(2-hydroxyethyl)ammonium acetate, trimethyl(2-hydroxyethyl)ammonium benzoate, trimethyl(2-hydroxyethyl)ammonium phthalate, tetraethyl ammonium formate, tetraethyl ammonium acetate, tetrapropyl ammonium formate, tetrapropyl ammonium acetate, tetrabutyl ammonium formate, tetrabutyl ammonium acetate, tetramethyl ammonium borate, tetramethyl ammonium phosphate, tetramethyl ammonium sulfate, trimethyl(2-hydroxyethyl)ammonium borate, trimethyl(2-hydroxyethyl)ammonium phosphate and trimethyl(1-hydroxyethyl)ammonium sulfate.
The concentration of the quarternary ammonium salt in the cleaning agent for the semiconductor device according to the present invention is within a range of from 1 to 60% by weight, preferably 10 to 50% by weight. If the concentration of the quarternary ammonium salt is less than 1% by weight, violent corrosion occurs in the wiring material whereas if it is more than 60% by weight, the removing rate for the side wall protecting deposition film is lowered, which is not desirable.
As the fluoro compound in the cleaning agent for the semiconductor device according to the present invention there can be mentioned, for example, hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, ammonium borofluoride, tetramethyl ammonium fluoride and tetramethyl ammonium hydrogen fluoride.
The concentration of the fluoro compound is from 0.1 to 10% by weight, preferably 0.5 to 5% by weight. If the concentration of the fluoro compound is less than 0.1% by weight, the removing rate for the side wall protecting deposition film is lower, whereas violent corrosion occurs to the wiring material at a concentration higher than 10% by weight.
As the organic solvent added further in the present invention, there can be mentioned amides such as dimethyl formamide, dimethyl acetamide, formamide and N-methyl pyrrolidone, lactones such as  butyrolactone, nitriles such as acetonitrile and benzonitrile, alcohol such as methanol, ethanol, isopropanol and ethylene glycol and esters such as methyl acetate, ethyl acetate an d methyl benzoate.
The concentration of the organic solvent is from 1 to 60% by weight, preferably 20 to 55% by weight. If the concentration of the organic solvent is less than 1% by weight, violent corrosion occurs to the wiring material, whereas the removing rate for the side wall protecting deposition film is lowered at a concentration higher than 60% by weight.
The temperature for the cleaning agent for the semiconductor device according to the present invention upon removing the side wall protecting deposition film is usually at a normal temperature, for example, 18 to 25xc2x0 C. If the removing rate for the side wall protecting deposition film is remarkably low, the cleaning agent should be heated, for example, at 25 to 60xc2x0 C. Further, the cleaning temperature and the cleaning time are properly selected considering the state of the side wall protecting deposition film and the kind of the wiring materials.
Upon peeling of the side wall protecting deposition film by cleaning, the peeling step employs a method used so far by the cleaning according to the present invention for the semiconductor substrate to be processed. For example, dipping cleaning by batch system or spray or jet cleaning for each substrate and then cleaning with purified water and drying are applied by the above-mentioned system to complete the process.